Just dye a simple black or dark brown, do well for the interview and hope you get the job. After you got the job, do well, pass probation, build good relationship with your boss and colleagues, then you are free to dye it to lighter shades of brown. No matter what job (unless you interviewing for hair stylist or fashion blogger), first impression counts. Without knowing exactly what kind of culture the department is and the personality of your hiring manager, the safest thing you can do is to be subtle and simple in how you look. If you need references, go to the website of the organisation you are interviewing for, usually they will have pictures of people in their website in the career page, those images are style that your should follow.

Good luck.